Optical magnifier suitable for use with a microdisplay device

ABSTRACT

An optical magnifier is provided. One general form of one example embodiment includes two lens elements, at least two aspheric surfaces, and at least one diffractive surface. Another general form of another example embodiment includes three lens elements, and at least three aspheric surfaces. At least two of the aspheric surfaces can be simple conics. The optical magnifier, suitable for use in an electronic display system, has an apparent field of view of at least +/−10 degrees; a magnification of at least 15×; a back focal length of at least 5 mm; and an eye relief greater than the effective focal length of the optical magnifier. The lens elements can be made from plastic.

FIELD OF THE INVENTION

[0001] This invention relates generally to optical systems and inparticular to optical magnifiers incorporated into and/or used inconjunction with other optical components.

BACKGROUND OF THE INVENTION

[0002] Optical Magnifiers (also referred to as “eyepieces” or “loupes”)are known. Typically, these optical devices are used to allow directviewing of slides or other small objects or are used as part of otheroptical systems such as, for example, telescopes and viewfinders.

[0003] Conventional optical magnifiers utilize magnifier lenses thatprovide an enlarged virtual image of a real object in front of aviewer's eye. It is generally preferable that such lenses, incombination with the object being viewed, provide an apparent field ofview to the user in excess of +/−10 degrees, in order to avoid thesensation of “tunnel vision”. Additionally, these magnifier lensespreferably provide a relatively long eye relief (that is, the distanceat which the lens can be held from the eye) in order to allow an objectto be comfortably viewed.

[0004] Optical magnifiers have also been suggested for viewingelectronic displays incorporated, for example, in portable electronicdevices. When used to view electronic displays, the same criteria,described above, applies, even though newer high quality micro-displaysare now being manufactured with full diagonals of 6 mm or less. In orderto obtain a +/−10 degree apparent field of view, such smallmicro-displays require a high magnification lens (on the order of 15× orgreater), which translates to an effective focal length of approximately17 mm or less. As is known, magnification for this type of opticalsystem is calculated using the standard formula: M=254 mm/EFL, where EFLis the effective focal length of the lens, measured in mm.

[0005] For comfortable viewing by users, including those wearingeyeglasses, it is generally accepted that a reasonable eye relief isapproximately 17 mm or greater. As such, in the relative sense, the eyerelief should preferably be at least as great as the EFL of the lens(for example, 17 mm in the 15×example described above) formicro-displays of this size. This relationship between eye relief andEFL becomes even more of a concern when shorter focal length (highermagnification) systems are contemplated. This is a new and challenginggoal that did not previously exist for larger electronic displays usedwith correspondingly lower magnification lenses.

[0006] In U.S. Pat. No. 4,094,585, E. I. Betensky discloses athree-element all-plastic optical magnifier comprising from the viewingend, a first positive lens group comprising a single element, and asecond lens group comprising a bi-convex element and a bi-concaveelement forming a doublet having the overall shape of a meniscus. Thismagnifier has a magnification in the range of 13×to 14×. Formicro-displays with full diagonals of less than 6 mm, this magnifierdoes not provide the desired +/−10 degree field of view. Additionally,this magnifier has the added labor expense of cementing two elements toform a doublet, which may be unacceptable for cost-sensitiveapplications.

[0007] In U.S. Pat. No. 5,835,279, I. Marshall and R. Holmes disclose athree-element all-plastic magnifier lens for viewing an LCD in thebinocular vision system of a head-mounded display unit. This design hasa large (+/−35.8 degree) apparent field of view and a long (17 mm) eyerelief. However, the LCD is quite large (33.65 mm full diagonal) and theresulting magnification is only about 11×, making it unsuitable for usewith micro-displays of the scale contemplated here. Additionally, whenthis system is scaled to a magnification of 15×, the eye relief drops toabout 12.4 mm, quite short for users wearing eyeglasses.

[0008] In U.S. Pat. Nos. 5,909,322 and 5,886,825, J. R. Bietry disclosestwo- and three-element plastic designs for magnifier lenses suitable foruse in liquid crystal (LCD) or light emitting diode (LED) micro-displaysystems. Although these lenses have a magnification of 16×, high imagequality, and long eye relief, these designs contain at least onediffractive surface, for both the two element and three element formsand/or include a rear meniscus lens which is concave toward the objectand positionable within 5 mm of the object surface. As a number of newer“micro-display” devices, for example, LCD devices, depend on light beingdelivered from the front of the display via a polarizing beam splittingdevice, a back focal length (BFL) of the lens in excess of 5 mm is oftenessential for the placement of the optical magnifier. For micro-displayswhich require a BFL in excess than 5 mm, these designs will simply notfunction.

SUMMARY OF THE INVENTION

[0009] According to one aspect of the present invention, a magnifierlens comprises in order from an eye side a first positive power meniscuslens element having an eye side surface and an object side surface withat least one of the eye side surface and the object side surface isaspheric; and a second positive power lens element having an asphericobject side surface convex toward the object side and an eye sidesurface, wherein at least one of the object side surface of the firstpositive power meniscus element and the eye side surface of the secondpositive power element is diffractive.

[0010] According to another aspect of the invention, an optical systemcomprises in order from an eye side a first positive power meniscus lenselement having an eye side surface and an object side surface with atleast one of the eye side surface and the object side surface beingaspheric; a second positive power lens element having an aspheric objectside surface convex toward the object side and an eye side surface,wherein at least one of the object side surface of the first positivepower meniscus element and the eye side surface of the second positivepower element is diffractive; and an object to be viewed.

[0011] According to another aspect of the invention, a magnifier lenscomprises in order from an eye side a first positive power lens elementhaving an aspheric eye side surface; a second negative power meniscuslens element having an aspheric object side surface; and a thirdpositive power bi-convex lens element having at least one asphericsurface.

[0012] According to another aspect of the invention, an optical systemcomprises in order from an eye side a first positive power lens elementhaving an aspheric eye side surface; a second negative power meniscuslens element having an aspheric object side surface; a third positivepower bi-convex lens element having at least one aspheric surface; andan object to be viewed.

[0013] According to another aspect of the invention, a magnifier lenscomprises in order from an eye side a first positive power lens elementhaving an aspheric surface; and a second positive power lens elementhaving an aspheric surface, the magnifier lens having a back focallength in air, wherein the back focal length of the magnifier lens inair is greater than 5 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the detailed description of the preferred embodiments of theinvention presented below, reference is made to the accompanyingdrawings, in which:

[0015]FIG. 1 shows a sectional view of a first embodiment of themagnifier lens system of the first general form;

[0016]FIG. 2 shows a sectional view of a second embodiment of themagnifier lens system of the first general form;

[0017]FIG. 3 shows a sectional view of a third embodiment of themagnifier lens system of the first general form;

[0018]FIG. 4 shows a sectional view of a fourth embodiment of themagnifier lens system of the first general form;

[0019]FIG. 5 shows a sectional view of a first embodiment of themagnifier lens system of the second general form;

[0020]FIG. 6 shows a sectional view of a second embodiment of themagnifier lens system of the second general form;

[0021]FIG. 7 shows a sectional view of a third embodiment of themagnifier lens system of the second general form;

[0022]FIG. 8 shows a plot of the through-focus Modulation TransferFunction (MTF) of the magnifier lens illustrated in FIG. 1, the MTF ispolychromatic (with equal weights of 510, 560, 610 nm light) at aspatial frequency of 21 line pairs/mm;

[0023]FIG. 9 shows a plot of the through-focus Modulation TransferFunction (MTF) of the magnifier lens illustrated in FIG. 2, the MTF ispolychromatic (with equal weights of 510, 560, 610 nm light) at aspatial frequency of 21 line pairs/mm;

[0024]FIG. 10 shows a plot of the through-focus Modulation TransferFunction (MTF) of the magnifier lens illustrated in FIG. 3, the MTF ispolychromatic (with equal weights of 510, 560, 610 nm light) at aspatial frequency of 21 line pairs/mm;

[0025]FIG. 11 shows a plot of the through-focus Modulation TransferFunction (MTF) of the magnifier lens illustrated in FIG. 4, the MTF ispolychromatic (with equal weights of 510, 560, 610 nm light) at aspatial frequency of 21 line pairs/mm;

[0026]FIG. 12 shows a plot of the through-focus Modulation TransferFunction (MTF) of the magnifier lens illustrated in FIG. 5, the MTF ispolychromatic (with equal weights of 510, 560, 610 nm light) at aspatial frequency of 21 line pairs/mm;

[0027]FIG. 13 shows a plot of the through-focus Modulation TransferFunction (MTF) of the magnifier lens illustrated in FIG. 6, the MTF ispolychromatic (with equal weights of 510, 560, 610 nm light) at aspatial frequency of 21 line pairs/mm; and

[0028]FIG. 14 shows a plot of the through-focus Modulation TransferFunction (MTF) of the magnifier lens illustrated in FIG. 7, the MTF ispolychromatic (with equal weights of 510, 560, 610 nm light) at aspatial frequency of 21 line pairs/mm.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The present description will be directed in particular toelements forming part of, or cooperating more directly with, apparatusin accordance with the present invention. It is to be understood thatelements not specifically shown or described may take various forms wellknown to those skilled in the art.

[0030] In the following descriptions of example embodiments of theinvention, the term magnifier lens is used to describe an opticalsystem. However, a person skilled in the art will understand that themagnifier lens(s) described herein can be used as, for example, aneyepiece with other optical components. As such, the term magnifier lensshould not be considered limited to any particular application. Note,that since that light can be directed through the magnifier lens in anydirection, the eye position can be replaced by a galvanometer or arotating polygon with some minor distortion adjustments. Thus, amagnifier lens constructed according to the present invention can beused, for example, in scanner applications. The magnifier lens can alsobe used as part of a viewfinder system in, for example, a digital orhybrid (digital/film) camera to image a scene displayed on an electronicdisplay to a user's eye for preview and/or review.

[0031] Referring to FIGS. 1-7, the terms “front” and “rear” refer to theeye side and object side of the magnifier lens, respectively. In thefollowing examples, 10 is the diaphragm of an eye or other instrument,20 is a polarizing beam splitter (PBS) or other suitable device fordividing light rays, and 30 is a cover plate protecting an object to beviewed (for example, an image display) 40. The PBS 20 is preferably apartially transmissive/partially reflective device used to illuminatethe display front-on via a light source located out of the optical pathof the magnifier. Typically, in practice, the PBS 20 (or other beamsplitting device, or other light dividing device, etc.) is onlynecessary for objects to be viewed (for example, image displays) 40 thatrequire front-on illumination.

[0032] Although the PBS 20 is shown here as perpendicular to the opticalaxis 60 of the optical system 50, the PBS 20 is typically tilted at someangle or curved along at least one dimension or both. Additionally, thecorrection of aberrations due to this non-axially symmetric componentwould require at least one additional non-axially symmetric feature orcomponent. For these reasons, and with simplicity and cost of theoptical system 50 in mind, no attempt to correct aberrations associatedwith the PBS was made other than inserting the PBS 20 as a thin flatplate oriented perpendicular to the optical axis 60.

[0033] The example embodiments of the invention are illustrated in FIGS.1-7, and Tables 1-7, respectively. In FIGS. 1-7 and Tables 1-7, thesurface radii R are numbered beginning at the front side of themagnifier lens 70 ending at the surface of the object to be viewed (forexample, an image display surface) 40. In Tables 1-7, the thicknesses ofthe lens elements and the airspaces between the lens elements are bothlabeled as “thickness” and are listed on the same line as the surfacepreceding the thickness. For example, the first thickness in Table 1corresponds to the distance from the eye diaphragm to the first surfaceof the first element E₁. Similarly, the second thickness in Table 1corresponds to the thickness of the first element E₁ in the system. Allthicknesses provided in Tables 1-7 are in millimeters. All indices andV-numbers (also known as Abbe numbers) are for the helium d line of thespectrum at a wavelength of 587.6 nm. Additionally, the exampleembodiments are color-corrected for the visible spectrum by modeling thephotopic response of the human eye using equal weights of 510, 560, and610 nm light.

[0034] A magnifier lens 70 of a first example embodiment is depicted inFIG. 1. This magnifier lens 70 includes two lens elements E₁ and E₂. Thefirst lens element E₁ is a positive power meniscus element concavetoward the rear, object side. The front, eye side surface of element E₁is aspheric and the rear, object side surface of element E₁ isspherical. The second lens element E₂ is a positive power meniscus lenselement as well. The front, eye side surface of element E₂ is adiffractive and the rear, object side surface of element E₂ is aspheric.Elements E₁ and E₂ are made of plastic and can be molded. The totalthickness of the magnifier lens 70, including elements E₁ and E₂ and theairspace between them, is about 8.6 mm. The total thickness from thefront, eye side surface of E₁ to the surface of the object to be viewed(for example, an image display surface) 40 is about 16.7 mm.

[0035] A magnifier lens 70 of a second example embodiment is depicted inFIG. 2. This magnifier lens 70 includes two lens elements E₁ and E₂. Thefirst lens element E₁ is a positive power meniscus element concavetoward the rear, object side. The front, eye side surface of element E₁is spherical and the rear, object side surface of element E₁ isaspheric. The second lens element E₂ is a positive power meniscus lenselement as well. The front, eye side surface of element E₂ is adiffractive and the rear, object side surface of element E₂ is aspheric.Elements E₁ and E₂ are made of plastic and can be molded. The totalthickness of the magnifier lens 70, including elements E₁ and E₂ and theairspace between them, is about 8.6 mm. The total thickness from thefront, eye side surface of E₁ to the surface of the object to be viewed(for example, an image display surface) 40 is about 16.9 mm.

[0036] A magnifier lens 70 of a third example embodiment is depicted inFIG. 3. This magnifier lens 70 includes two lens elements E₁ and E₂. Thefirst lens element E₁ is a positive power meniscus element concavetoward the rear, object side. The front, eye side surface of element E₁is aspheric and the rear, object side surface of element E₁ isdiffractive. The second lens element E₂ is a positive power meniscuslens element as well. The front, eye side surface of element E₂ isspherical and the rear, object side surface of element E₂ is aspheric.Elements E₁ and E₂ are made of plastic and can be molded. The totalthickness of the magnifier lens 70, including these two elements and theairspace between them, is about 8.1 mm. The total thickness from thefront, eye side surface of E₁ to the surface of the object to be viewed(for example, an image display surface) 40 is about 16.2 mm.

[0037] A magnifier lens 70 of a fourth example embodiment is depicted inFIG. 4. This magnifier lens 70 includes two lens elements E₁ and E₂. Thefirst lens element E₁ is a positive power meniscus element concavetoward the rear, object side. The front, eye side surface of element E₁is aspheric and the rear, object side surface of element E₁ isdiffractive. The second lens element E₂ is a positive power bi-convexlens element. The front, eye side surface of element E₂ is spherical andthe rear, object side surface of element E₂ is aspheric. Elements E₁ andE₂ are made of plastic and can be molded. The total thickness of themagnifier lens 70, including these two elements and the airspace betweenthem, is about 8.4 mm. The total thickness from the front, eye sidesurface of E₁ to the surface of the object to be viewed (for example, animage display surface) 40 is about 16.5 mm.

[0038] A magnifier lens 70 of a fifth example embodiment is depicted inFIG. 5. This magnifier lens 70 includes three lens elements E₁, E₂, andE₃. The first lens element E₁ is a positive power bi-convex element. Thefront, eye side surface of element E₁ is aspheric (simple conic) and therear, object side surface of element E₁ is spherical. The second lenselement E₂ is a negative power meniscus lens element convex toward theeye side. The front, eye side surface of element E₂ is spherical and therear, object side surface of element E₂ is aspheric (simple conic). Thethird lens element E₃ is a positive power bi-convex element. The front,eye side surface of element E₃ is spherical and the rear, object sidesurface of element E₃ is aspheric. Elements E₁, E₂, and E₃ are made ofplastic and can be molded. The total thickness of the magnifier lens 70,including these three elements and the airspaces between them, is about9.8 mm. The total thickness from the front, eye side surface of E₁ tothe surface of the object to be viewed (for example, an image displaysurface) 40 is about 17.9 mm.

[0039] A magnifier lens 70 of a sixth example embodiment is depicted inFIG. 6. This magnifier lens 70 includes three lens elements E₁, E₂, andE₃. The first lens element E₁ is a positive power meniscus element,convex toward the eye side. The front, eye side surface of element E₁ isaspheric and the rear, object side surface of element E₁ is spherical.The second lens element E₂ is a negative power meniscus lens elementconvex toward the eye side. The front, eye side surface of element E₂ isspherical and the rear, object side surface of element E₂ is aspheric(simple conic). The third lens element E₃ is a positive power bi-convexelement. The front, eye side surface of element E₃ is spherical and itsrear, object side surface is aspheric. Elements E₁, E₂, and E₃ are madeof plastic and can be molded. The total thickness of the magnifier lens70, including these three elements and the airspaces between them, isabout 9.5 mm. The total thickness from the front, eye side surface of E₁to the surface of the object to be viewed (for example, an image displaysurface) 40 is about 17.2 mm.

[0040] A magnifier lens 70 of a seventh example embodiment is depictedin FIG. 7. This magnifier lens 70 includes three lens elements E₁, E₂,and E₃. The first lens element E₁ is a positive power bi-convex element.The front, eye side surface of element E₁ is aspheric (simple conic) andthe rear, object side surface of element E₁, is spherical. The secondlens element E₂ is a negative power meniscus lens element convex towardthe eye side. The front, eye side surface of element E₂ is spherical andthe rear, object side surface of element E₂ is aspheric (simple conic).The third lens element E₂ is a positive power bi-convex element. Thefront, eye side surface of element E₃ is aspheric and the rear, objectside surface of element E₃ is spherical. Elements E₁, E₂, and E₃ aremade of plastic and can be molded. The total thickness of the magnifierlens 70, including these three elements and the airspaces between them,is about 9.3 mm. The total thickness from the front, eye side surface ofE₁ to the surface of the object to be viewed (for example, an imagedisplay surface) 40 is about 17.6 mm.

[0041] The seven example embodiments described above are designed for anobject semi-diagonal of 2.4 mm. These embodiments have effective focallengths between 12.87 mm and 13.05 mm and corresponding magnificationsbetween 19.7× and 19.5×, respectively. Embodiments 1-7 have an apparentfield of view of +/−10.5 degrees, an eye relief of 17 mm, and assume apupil diameter of 6 mm. The resulting relative aperture of embodiments1-7 is about f/2.2. The seven example embodiments have a maximumdistortion (absolute value)<1% and a primary lateral chromaticaberration (absolute value)<3 microns. Additionally, any one or all ofthe individual lens elements described above can be made using glass inconjunction with a grinding and polishing or molding manufacturingprocess.

[0042] The embodiments described above are suitable for use withLCD-type micro-displays. This is made possible by designing themagnifier lenses 70 to be approximately telecentric on the display side(i.e., chief rays nearly parallel to the optical axis of the system,which is itself parallel to the display surface normal). It is knownthat doing so reduces perceived brightness falloff toward the corners ofthe display (which can be substantial with non-telecentric lenses). Inembodiments 1-7, the maximum chief ray angle (absolute value) on thedisplay side for all of these embodiments is <3 degrees. Additionally,the embodiments described above are suitable for use with other types ofelectronic displays and micro-displays, for example, light emittingdiode displays such as organic light emitting diode displays, polymericlight emitting diode displays, etc.

[0043] Additionally, embodiments 1-7 employ vignetting at the front, eyeside surface of the first element E₁. Vignetting stops some aberratedrays near the edge of the pupil from reaching off-axis points in theimage plane. This increases off-axis image quality at the expense ofreduced illumination in the corners of the image relative to that at thecenter of the image (i.e., relative illumination). Vignetting in thecorner of the image is between 25% and 35% for the embodiments describedabove. This is well within the (generally accepted) 30-40% vignettingthat the human eye can tolerate before it becomes noticeable.

[0044] It is well known by those skilled in the art of magnifier designthat the human eye can accommodate some degree of field curvature byeffectively refocusing (the eye) for different parts of the field. Theeye can also tolerate some (typically, lesser) degree of astigmatism.Traditionally, when the tangential and sagittal field curves all liewithin 1 diopter of the central focus, the image is reasonably welldefined over the field. Also, in the absence of astigmatism, a youngobserver can focus on the field edge and accommodate about 3 dioptersfor the center. In embodiments 1-7, the image is permitted to curvesomewhat, thereby facilitating the reduction of astigmatism in themagnifier lenses 70. The result is essentially just some degree of fieldcurvature (from the lenses) and the astigmatism associated with the PBS20. For the embodiments described above, the curvature of the fieldcorresponds to an accommodation of <0.6 diopters between the center andthe edge of the field.

[0045] The through-focus MTF plots shown in FIGS. 8-14 are polychromatic(equal weights of 510 nm, 560 nm, and 610 nm light) for the embodimentsdepicted in FIGS. 1-7, and Tables 1-7, respectively. The MTF plots areshown for 21 line pairs/mm, half the nyquist frequency for a displaywith 0.012 mm square pixels. Each MTF plot assumes a curved imagesurface with radius as given in the prescriptions of Tables 1-7.

[0046] It should be noted that for the embodiments in FIGS. 5-7 andTables 5-7, respectively, the polychromatic MTF performance issubstantially the same for equal weights of 450 nm, 550 nm, and 650 nm.For the embodiments in FIGS. 1-4 and Tables 1-4, respectively, thepolychromatic MTF performance drops somewhat for equal weights of 450nm, 550 nm, and 650 nm, but may be recovered quite well with a quickre-optimization. TABLE 1 CLEAR SURF. APER. RADIUS THICKNESS INDEXV-NUMBER 6.00 DIAPHRAGM 17.000 1 10.20* ASPHERE(1) 3.710 1.492 57.8 29.14   16.4892 1.900 3 8.62 −22.2252(2) 2.972 1.590 30.8 4 7.90ASPHERE(1) 2.443 5 6.79 PLANO 0.330 1.550 55.0 6 6.71 PLANO 4.635 7 4.93PLANO 0.725 1.570 55.0 8 4.82 −30.5417 *DO NOT EXCEED LENS LENGTH 8.582NOTES: 1) ASPHERIC SURFACE DESCRIBED BY SAG EQUATION:${X(Y)} = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)C^{2}Y^{2}}}} + {DY}^{4} + {EY}^{6} + {FY}^{8} + {GY}^{10} + {HY}^{12}}$

SURF. 1 C = 0.1666667 D = −0.28952730E−03 F = −0.93959591E−06 k =0.0000000 E = 0.90649168E−05 G = 0.35556391E−07 VERTEX RADIUS (1/C) =6.0000 H = −0.57183989E−09 SURF. 4 C = −0.0897376 D = 0.79693786E−03 F =0.24127936E−05 k = 0.0000000 E = 0.16847998E−05 G = −0.17226572E−06VERTEX RADIUS (1/C) = −11.1436 H = 0.65623726E−08 2) DIFFRACTIVE SURFACEDESCRIBED BY PHASE EQUATION:${\Phi (Y)} = {\frac{2\pi}{\lambda_{0}}\left( {{C_{1}Y^{2}} + {C_{2}Y^{4}} + {C_{3}Y^{6}} + {C_{4}Y^{8}}} \right)}$

SURF. 3 λ₀ = 560 N C₁ = −4.12013E−03 C₃ = −3.46267E−06 C₂ = 7.96815E−05C₄ = 1.07025E−07

[0047] TABLE 2 CLEAR SURF. APER. RADIUS THICKNESS INDEX V-NUMBER 6.00DIAPHRAGM 17.000 1 10.20*    6.229 3.851 1.492 57.8 2 9.11 ASPHERE(1)1.807 3 8.69 −31.0221(2) 2.946 1.590 30.8 4 8.14 ASPHERE(1) 2.594 5 6.82PLANO 0.330 1.550 55.0 6 6.74 PLANO 4.635 7 4.93 PLANO 0.725 1.570 55.08 4.82 −30.5417 *DO NOT EXCEED LENS LENGTH 8.604 NOTES: 3) ASPHERICSURFACE DESCRIBED BY SAG EQUATION:${X(Y)} = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)C^{2}Y^{2}}}} + {DY}^{4} + {EY}^{6} + {FY}^{8} + {GY}^{10} + {HY}^{12}}$

SURF. 2 C = 0.4044146 D = 0.52788255E−03 F = 0.48822016E−06 k =0.0000000 E = −0.51777047E−05 G = −0.48083647E−07 VERTEX RADIUS (1/C) =24.7241 H = 0.36767183E−09 SURF. 4 C = −0.1093386 D = 0.64198372E−03 F =0.35968081E−05 k = 0.0000000 E = −0.11253640E−04 G = −0.21871596E−06VERTEX RADIUS (1/C) = −9.1459 H = 0.74093706E−08 4) DIFFRACTIVE SURFACEDESCRIBED BY PHASE EQUATION:${\Phi (Y)} = {\frac{2\pi}{\lambda_{0}}\left( {{C_{1}Y^{2}} + {C_{2}Y^{4}} + {C_{3}Y^{6}} + {C_{4}Y^{8}}} \right)}$

SURF. 3 λ₀ = 560 N C₁ = −4.06429E−03 C₃ = −3.73155E−06 C₂ = 7.15512E−05C₄ = 1.62241E−07

[0048] TABLE 3 CLEAR SURF. APER. RADIUS THICKNESS INDEX V-NUMBER 6.00DIAPHRAGM 17.000 1 10.20* ASPHERE(1) 4.091 1.492 57.8 2 8.95  19.2401(2) 1.264 3 8.57 −39.0234 2.750 1.590 30.8 4 7.56 ASPHERE(1)2.441 5 6.63 PLANO 0.330 1.550 55.0 6 6.56 PLANO 4.635 7 4.92 PLANO0.725 1.570 55.0 8 4.82 −30.5417 *DO NOT EXCEED LENS LENGTH 8.582 NOTES:5) ASPHERIC SURFACE DESCRIBED BY SAG EQUATION:${X(Y)} = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)C^{2}Y^{2}}}} + {DY}^{4} + {EY}^{6} + {FY}^{8} + {GY}^{10} + {HY}^{12}}$

SURF. 1 C = 0.1646063 D = −0.20370475E−03 F = −0.70916812E−06 k =0.0000000 E = 0.86070374E−05 G = 0.24289232E−07 VERTEX RADIUS (1/C) =6.0751 H = −0.31512663E−09 SURF. 4 C = −0.0603912 D = 0.95297402E−03 F =0.62224391E−05 k = 0.0000000 E = −0.15864043E−04 G = −0.47132486E−06VERTEX RADIUS (1/C) = −16.5587 H = 0.17717982E−07 6) DIFFRACTIVE SURFACEDESCRIBED BY PHASE EQUATION:${\Phi (Y)} = {\frac{2\pi}{\lambda_{0}}\left( {{C_{1}Y^{2}} + {C_{2}Y^{4}} + {C_{3}Y^{6}} + {C_{4}Y^{8}}} \right)}$

SURF. 2 λ₀ = 560 N C₁ = −3.32269E−03 C₃ = −1.71275E−06 C₂ = 4.52118E−05C₄ = 5.78513E−08

[0049] TABLE 4 CLEAR SURF. APER. RADIUS THICKNESS INDEX V-NUMBER 6.00DIAPHRAGM 17.000 1 10.20* ASPHERE(1) 4.294 1.492 57.8 2 8.55   8.1991(2) 1.349 3 8.38 21.6332 2.750 1.590 30.8 4 7.62 ASPHERE(1)2.441 5 6.67 PLANO 0.330 1.550 55.0 6 6.59 PLANO 4.635 7 4.93 PLANO0.725 1.570 55.0 8 4.81 −30.5417 *DO NOT EXCEED LENS LENGTH 8.393 NOTES:7) ASPHERIC SURFACE DESCRIBED BY SAG EQUATION:${X(Y)} = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)C^{2}Y^{2}}}} + {DY}^{4} + {EY}^{6} + {FY}^{8} + {GY}^{10} + {HY}^{12}}$

SURF. 1 C = 0.1682086 D = −0.36386441E−03 F = −0.13188881E−05 k =0.0000000 E = 0.12936727E−04 G = 0.50574451E−07 VERTEX RADIUS (1/C) =5.945 H = −0.93964616E−09 SURF. 4 C = −0.0426814 D = 0.71989155E−03 F =0.27592984E−05 k = 0.0000000 E = −0.41520397E−05 G = −0.20084234E−06VERTEX RADIUS (1/C) = −23.4294 H = 0.85266176E−08 8) DIFFRACTIVE SURFACEDESCRIBED BY PHASE EQUATION:${\Phi (Y)} = {\frac{2\pi}{\lambda_{0}}\left( {{C_{1}Y^{2}} + {C_{2}Y^{4}} + {C_{3}Y^{6}} + {C_{4}Y^{8}}} \right)}$

SURF. 2 λ₀ = 560 N C₁ = −3.74332E−03 C₃ = 4.01070E−06 C₂ = −5.34761E−05C₄ = −4.14056E−08

[0050] TABLE 5 CLEAR SURF. APER. RADIUS THICKNESS INDEX V-NUMBER 6.00DIAPHRAGM 17.000 1 9.10* ASPHERE(1) 3.380 1.492 57.8 2 8.73 −104.38230.181 3 8.52 32.1466 1.449 1.583 30.1 4 7.57 ASPHERE(1) 1.053 5 7.996.9618 3.698 1.492 57.8 6 7.85 ASPHERE(1) 2.444 7 6.73 PLANO 0.330 1.55055.0 8 6.66 PLANO 4.635 9 4.95 PLANO 0.725 1.570 55.0 10 4.82 −28.7621*DO NOT EXCEED LENS LENGTH 9.761 NOTES: 1) ASPHERIC SURFACE DESCRIBED BYSAG EQUATION:${X(Y)} = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)C^{2}Y^{2}}}} + {DY}^{4} + {EY}^{6} + {FY}^{8} + {GY}^{10} + {HY}^{12}}$

SURF. 1 C = 0.1582487 D = 0.0000000E+00 F = 0.0000000E+00 k = −0.2126760E = 0.0000000E+00 G = 0.0000000E+00 VERTEX RADIUS (1/C) = 6.3194 H =0.0000000E+00 SURF. 4 C = 0.2284044 D = 0.0000000E+00 F = 0.0000000E+00k = −0.7743398 E = 0.0000000E+00 G = 0.0000000E+00 VERTEX RADIUS (1/C) =4.3782 H = 0.000000E+00 SURF. 6 C = −0.0868644 D = 0.4399801E−03 F =−0.3529413E−06 k = 0.0000000 E = 0.4799854E−05 G = 0.8495183E−08 VERTEXRADIUS (1/C) = −11.5122 H = 0.0000000E−00

[0051] TABLE 6 CLEAR SURF. APER. RADIUS THICKNESS INDEX V-NUMBER 6.00DIAPHRAGM 17.000 1 9.10* ASPHERE(1) 3.188 1.492 57.8 2 8.69 95.48450.335 3 8.50 26.9536 1.280 1.583 30.1 4 7.66 ASPHERE(1) 0.744 5 7.827.1693 3.314 1.492 57.8 6 7.61 ASPHERE(1) 2.657 7 6.56 PLANO 0.330 1.55055.0 8 6.49 PLANO 4.635 9 4.94 PLANO 0.725 1.570 55.0 10 4.82 −28.900*DO NOT EXCEED LENS LENGTH 8.861 NOTES: 2) ASPHERIC SURFACE DESCRIBED BYSAG EQUATION:${X(Y)} = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)C^{2}Y^{2}}}} + {DY}^{4} + {EY}^{6} + {FY}^{8} + {GY}^{10} + {HY}^{12}}$

SURF. 1 C = 0.1627657 D = −0.9597174E−05 F = 0.8515111E−07 k =−01.0784800 E = 0.6443622E−07 G = −0.8389589E−09 VERTEX RADIUS (1/C) =6.1438 H = 0.0000000E+00 SURF. 4 C = 0.2147075 D = 0.0000000E+00 F =0.0000000E+00 k = −0.9062283 E = 0.0000000E+00 G = 0.0000000E+00 VERTEXRADIUS (1/C) = 4.6575 H = 0.000000E+00 SURF. 6 C = −0.0832591 D =0.6436675E−03 F = −0.3216570E−06 k = 0.0000000 E = 0.7271238E−05 G =0.2184924E−07 VERTEX RADIUS (1/C) = −12.0107 H = 0.0000000E−00

[0052] TABLE 7 CLEAR SURF. APER. RADIUS THICKNESS INDEX V-NUMBER 6.00DIAPHRAGM 17.000 1 9.10* ASPHERE(1) 3.339 1.492 57.8 2 8.74 −224.84690.210 3 8.54 26.8436 1.423 1.583 30.1 4 7.61 ASPHERE(1) 0.939 5 7.85ASPHERE(1) 3.574 1.492 57.8 6 7.71 −16.4096 2.444 7 6.64 PLANO 0.3301.550 55.0 8 6.56 PLANO 4.635 9 4.91 PLANO 0.725 1.570 55.0 10 4.81−28.7621 *DO NOT EXCEED LENS LENGTH 9.485 NOTES: 3) ASPHERIC SURFACEDESCRIBED BY SAG EQUATION:${X(Y)} = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {k + 1} \right)C^{2}Y^{2}}}} + {DY}^{4} + {EY}^{6} + {FY}^{8} + {GY}^{10} + {HY}^{12}}$

SURF. 1 C = 0.1609088 D = 0.0000000E+00 F = 0.0000000E+00 k = −1.3568420E = 0.0000000E+00 G = 0.0000000E+00 VERTEX RADIUS (1/C) = 6.2147 H =0.0000000E+00 SURF. 4 C = 0.2735529 D = 0.0000000E+00 F = 0.0000000E+00k = −1.5674930 E = 0.0000000E+00 G = 0.0000000E+00 VERTEX RADIUS (1/C) =3.6556 H = 0.000000E+00 SURF. 5 C = −0.2075765 D = −0.2473807E−02 F =0.6771738E−06 k = 0.0000000 E = −0.1801932E−04 G = −0.1057451E−06 VERTEXRADIUS (1/C) = 4.8616 H = 0.0000000E−00

[0053] The invention has been described in detail with particularreference to certain preferred embodiments thereof, but it will beunderstood that variations and modifications can be effected within thescope of the invention.

What is claimed is:
 1. A magnifier lens comprising in order from an eyeside: a first positive power meniscus lens element having an eye sidesurface and an object side surface, at least one of the eye side surfaceand the object side surface being aspheric; and a second positive powerlens element having an aspheric object side surface convex toward theobject side and an eye side surface, wherein at least one of the objectside surface of the first positive power meniscus element and the eyeside surface of the second positive power element is diffractive.
 2. Anoptical system comprising in order from an eye side: a first positivepower meniscus lens element having an eye side surface and an objectside surface, at least one of the eye side surface and the object sidesurface being aspheric; a second positive power lens element having anaspheric object side surface convex toward the object side and an eyeside surface, wherein at least one of the object side surface of thefirst positive power meniscus element and the eye side surface of thesecond positive power element is diffractive; and an object to beviewed.
 3. The optical system of claim 2, wherein a back focal length inair from the object side surface of the second positive power lenselement to the object to be viewed is no less than about 7.7 mm.
 4. Theoptical system of claim 2, further comprising: a cover glass positionedon an eye side of the object to be viewed; and a beam splitterpositioned between the object side surface of the second positive powerlens element and the cover glass, wherein the object side surface of thesecond positive power lens element is positioned about 8.1 mm from theobject to be viewed.
 5. The optical system of claim 2, wherein theobject to be viewed is an electronic display.
 6. The optical system ofclaim 5, wherein the electronic display is a liquid crystal display. 7.The optical system of claim 5, wherein the electronic display has a fulldiagonal of approximately 6 mm or less.
 8. The optical system of claim5, wherein the electronic display is a micro-display.
 9. The opticalsystem of claim 5, wherein the electronic display is a light emittingdiode display.
 10. The optical system of claim 9, wherein the lightemitting diode display is an organic light emitting diode display. 11.The optical system of claim 9, wherein the light emitting diode displayis a polymeric light emitting diode display.
 12. The optical system ofclaim 2, the first and second lens elements comprising a magnifier lenshaving an object side positioned proximate to the object to be viewed,wherein the magnifier lens is adapted to be approximately telecentric onthe object side of the magnifier lens.
 13. A magnifier lens comprisingin order from an eye side: a first positive power lens element having anaspheric eye side surface; a second negative power meniscus lens elementhaving an aspheric object side surface; and a third positive powerbi-convex lens element having at least one aspheric surface.
 14. Themagnifier of claim 13, wherein the aspheric surface of the firstpositive power element is a simple conic.
 15. The magnifier of claim 13,wherein the aspheric surface of the second negative power meniscus is asimple conic.
 16. An optical system comprising in order from an eyeside: a first positive power lens element having an aspheric eye sidesurface; a second negative power meniscus lens element having anaspheric object side surface; a third positive power bi-convex lenselement having at least one aspheric surface; and an object to beviewed.
 17. The optical system of claim 16, wherein a back focal lengthin air from the object side surface of the third positive powerbi-convex lens element to the object to be viewed is no less than about7.7 mm.
 18. The optical system of claim 16, further comprising: a coverglass positioned on an eye side of the object to be viewed; and a beamsplitter positioned between the object side surface of the secondpositive power lens element and the cover glass, wherein the object sidesurface of the third positive power bi-convex lens element is positionedabout 8.1 mm from the object to be viewed.
 19. The optical system ofclaim 16, wherein the object to be viewed is an electronic display. 20.The optical system of claim 19, wherein the electronic display is aliquid crystal display.
 21. The optical system of claim 19, wherein theelectronic display has a full diagonal of approximately 6 mm or less.22. The optical system of claim 19, wherein the electronic display is amicro-display.
 23. The optical system of claim 19, wherein theelectronic display is a light emitting diode display.
 24. The opticalsystem of claim 23, wherein the light emitting diode display is anorganic light emitting diode display.
 25. The optical system of claim23, wherein the light emitting diode display is a polymeric lightemitting diode display.
 26. The optical system of claim 16, the first,second, and third lens elements comprising a magnifier lens having anobject side positioned proximate to the object to be viewed, wherein themagnifier lens is adapted to be approximately telecentric on the objectside of the magnifier lens.
 27. A magnifier lens comprising in orderfrom an eye side: a first positive power lens element having an asphericsurface; and a second positive power lens element having an asphericsurface, the magnifier lens having a back focal length in air, whereinthe back focal length of the magnifier lens in air is greater than 5 mm.28. The magnifier lens of claim 27, wherein the back focal length in airis greater than or equal to 7.7 mm.
 29. The magnifier lens of claim 27,the magnifier lens having an eye relief and an effective focal length,wherein the eye relief is greater than the effective focal length. 30.The magnifier lens of claim 29, wherein the eye relief is greater than1.3 times the effective focal length.
 31. The magnifier lens of claim27, the magnifier lens having a magnification, wherein the magnificationis at least 15×.
 32. The magnifier lens of claim 31, wherein themagnification is greater than 19×.
 33. The magnifier lens of claim 27,the magnifier lens having an eye relief, wherein the eye relief is atleast 17 mm.
 34. The magnifier lens of claim 27, the magnifier lenshaving an apparent field of view, wherein the apparent field of view isat least +/−10 degrees.
 35. The magnifier lens of claim 27, wherein thefirst and second positive lens elements are made from plastic.
 36. Themagnifier lens of claim 27, further comprising: a negative power lenselement positioned between the first and second positive power lenselements, the negative power lens element having an aspheric surface.37. The magnifier lens of claim 36, wherein the negative power lenselement is made from plastic.
 38. The magnifier lens of claim 36,wherein at least two of the aspheric surfaces are simple conics.
 39. Themagnifier lens of claim 38, the first positive power lens element havingan eye side surface, the eye side surface being the simple conic. 40.The magnifier lens of claim 38, the second negative power lens elementhaving a object side surface, the object side surface being the simpleconic.
 41. The magnifier lens of claim 36, wherein the second negativepower lens element is meniscus.
 42. The magnifier lens of claim 36,wherein the third positive power lens element is bi-convex.
 43. Themagnifier lens of claim 36, the magnifier lens having an effective focallength, wherein the back focal length is greater than 0.38 times theeffective focal length.
 44. The magnifier lens of claim 36, themagnifier lens having an effective focal length, wherein the back focallength is greater than 0.59 times the effective focal length.
 45. Themagnifier lens of claim 36, each lens element of the magnifier lenshaving a center thickness and an edge thickness, wherein a ratio ofcenter thickness to edge thickness of each lens element is between 0.5and 2.0.
 46. The magnifier lens of claim 36, the magnifier lens having atotal thickness from the eye side surface of the first lens element to asurface of a viewable object, wherein the total thickness is less than17.9 mm.
 47. The magnifier lens of claim 36, the magnifier lens havingan effective focal length and a total thickness from the eye sidesurface of the first lens element to a surface of a viewable object,wherein the total thickness is less than 1.40 times the effective focallength.
 48. The magnifier lens of claim 27, wherein at least one of thepositive power lens elements includes a diffractive surface.
 49. Themagnifier lens of claim 48, the first positive power lens element havingan object side surface, wherein the diffractive is on the object sidesurface of the first positive power lens element.
 50. The magnifier lensof claim 48, the second positive power lens element having an eye sidesurface, wherein the diffractive is on the eye side surface of thesecond positive power lens element.
 51. The magnifier lens of claim 48,the second positive power lens element having an object side surface,wherein the object side surface of the second positive power lenselement is convex toward the object side.
 52. The magnifier lens ofclaim 51, wherein the object side surface of the second positive powerlens element is aspheric.
 53. The magnifier lens of claim 48, whereinthe first positive power lens element is meniscus.
 54. The magnifierlens of claim 48, wherein the second positive power lens element isbi-convex.
 55. The magnifier lens of claim 48, the diffractive surfacehaving zone spacing, wherein the zone spacing is at least 20 microns.56. The magnifier lens of claim 27, the magnifier lens having an objectside positionable proximate to an object to be viewed, wherein themagnifier lens is adapted to be approximately telecentric on the objectside of the magnifier lens.
 57. The magnifier lens of claim 27, themagnifier lens having an effective focal length, wherein the back focallength is greater than 0.38 times the effective focal length.
 58. Themagnifier lens of claim 27, the magnifier lens having an effective focallength, wherein the back focal length is greater than 0.59 times theeffective focal length.
 59. The magnifier lens of claim 27, each lenselement of the magnifier lens having a center thickness and an edgethickness, wherein a ratio of center thickness to edge thickness of eachlens element is between 0.9 and 2.1.
 60. The magnifier lens of claim 27,the magnifier lens having a total thickness from the eye side surface ofthe first lens element to a surface of a viewable object, wherein thetotal thickness is less than 17.0 mm.
 61. The magnifier lens of claim27, the magnifier lens having an effective focal length and a totalthickness from the eye side surface of the first lens element to asurface of a viewable object, wherein the total thickness is less than1.33 times the effective focal length.